Process for making polymeric particles

ABSTRACT

A particulate composition comprising particles which consist of a shell wall surrounding a hydrophilic core, wherein the shell wall is formed from a polymeric coacervate and wherein the particles comprise a polymeric amphipathic stabiliser. Also claimed is a process of producing a particulate composition comprising particles which consist of a shell wall surrounding a hydrophilic core, comprising the steps of a) forming an aqueous liquid that contains a wall building material that is capable of forming the shell wall by coacervation, b) dispersing the aqueous liquid into a water immiscible liquid, which comprises a stabilising substance to form a dispersion that comprises aqueous droplets dispersed in a continuous phase of water immiscible liquid, c) subjecting the dispersion to coacervation conditions, such that the wall building material coacervates at the surface of the aqueous doplets, characterised in that the stabilising substance comprises a polymeric amphipathic stabiliser. Preferably the particulate composition obtainable by the process contains an active ingredient and is used in a detergent composition. The active ingredient preferably comprises any of detergency building ingredients, a buffering system and/or a sequesterant and/or detergent builder. Citric acid is a particularly preferred active ingredient.

[0001] This invention relates to a novel process for making polymericparticles which consist of a shell surrounding a hydrophilic core whichmay be aqueous or anhydrous. Preferably the particles are additives foruse in detergent compositions, particularly for use home laundryoperations. In particular the invention concerns capsules containingencapsulated low molecular weight additives, such as buffering agents orsequesterants, which can be released either in the wash cycle or therinse cycle of a laundry operation and single pack detergentcompositions wherein the low molecular weight additives are designed tobe released in order to improve for instance, detergency, rinsing orconditioning etc.

[0002] It is known to include various low molecular weight ingredientsinto detergent formulations. These ingredients include buffering agents,which are used adjust the pH of the wash water in order to ensureoptimal efficiency. Typically such buffering agents include mixtures ofbases and weak acids. Other low molecular weight additives includesequesterants, which are able to remove metal ions from solution. Thismay be important, for instance where high concentrations of calcium ionsinterfere with detergency or for instance high levels of iron ions bringabout discoloration. Thus it may be necessary to include into the asequesterant which is compatible with the detergent formulation.Suitable sequesterants may include EDTA, EDDHA or citric acid.

[0003] Inclusion of buffering agents or in particular sequesterants intodetergent formulations, can interfere with other ingredients comprisedin the detergent formulations. This is particularly a problem in moderndetergent formulations which contain a complex mixture of many differentformulations. It would therefore be desirable to provide such lowmolecular weight additives in the form of delayed release components,such that the additives are only released during the wash or rinsecycles.

[0004] It is known to provide delayed release compositions by entrapmentof the active ingredients.

[0005] Entrapment of active ingredients can be achieved by a number ofprocesses. Some of these techniques involve forming a polymeric shellaround a central core or active ingredient. Other methods involvepreparing a matrix of polymeric material throughout which an activeingredient is distributed.

[0006] Various methods for making capsules have been proposed in theliterature. For instance it is known to encapsulate hydrophobic liquidsby dispersing the hydrophobic liquid into an aqueous medium containing amelamine formaldehyde pre-condensate and then reducing the pH resultingin an impervious aminoplast resin shell wall surrounding the hydrophobicliquid. Variations of this type of process are described inGB-A-2073132, AU-A-27028/88 and GB-A-1507739, in which the capsules arepreferably used to provide encapsulated inks for use in pressuresensitive carbonless copy paper. Generally these capsules are designedto release the core material, when the shall wall is ruptured byexternal forces, e.g. by compression. Such a release method would beunsuitable for using a a detergent composition.

[0007] Typical techniques for forming a polymer shell are described in,for instance, GB 1,275,712, 1,475,229 and 1,507,739, DE 3,545,803 andU.S. Pat. No. 3,591,090. Generally these processes employ a continuousaqueous phase into which the shell forming materials are dissolved.

[0008] In U.S. Pat. No. 3,838,007 droplets of enzyme dispersed in anaqueous solution of, for instance, gelatin are dispersed into water andthen cross-linked, to give cross linked particles of the gelatincontaining the enzyme.

[0009] In EP-A-356,240 processes for encapsulating enzyme or otherbiologically produced material; in a matrix of polymeric material bymixing the polymeric material with aqueous liquor containing thebiologically produced material, dispersing this mixture in a waterimmiscible liquid and azeotroping the dispersion. The product can eitherbe relatively coarse beads that can be recovered or a stable dispersionof small particles in the water immiscible liquid.

[0010] In EP-A-356,239 there is a description of various compositionsand processes primarily intended for the encapsulation of enzymes forliquid or other detergents. One type of product described thereincomprises particles having a core comprising matrix polymer containingthe enzyme, oil around the core and a polymer shell around the oil.

[0011] Particles of a matrix polymer containing an active ingredient canbe formed as a dispersion in oil and this dispersion can then bedispersed in aqueous solution of an encapsulating polymer or blend ofpolymers and polymer deposition can then be caused to occur around theoil particles that contain the particles of matrix polymer that containthe active ingredient.

[0012] U.S. Pat. No. 5,744,152 describes a process for forming polymerparticles introduced as a solution of a water soluble salt with avolatile amine of a polymer that is relatively insoluble andnon-swelling in acid throughout which the active ingredient is dispersedor dissolved, and which the solution is heated to form the dry matrixand to volatilise the amine and thereby form a polymer that is insolublein acid. The release of an active ingredient can be controlled bycareful adjustment of the pH. This method is specifically designed forthe entrapment of relatively large sized ingredients, in particularenzymes, fungi, spores, bacteria, cells or antibiotics, which arereleased by pH adjustment as a suitable release mechanism. This processdoes not provide capsules, but instead produces a matrix of polymerthroughout which the active ingredients is ditributed.

[0013] WO 97/24178 describes a particulate composition comprisesparticles having a polymeric matrix including a detergency activeingredient, wherein the polymeric matrix is formed of a free base formof a cationic polymer which is a co-polymer of an ethylenicallyunsaturated hydrophobic monomer with an ethylenically unsaturatedsubstituted amine monomer. The matrix particles can be made bypolymerising the free base monomer and the hydrophobic monomer whiledissolved in an organic solvent so as to form a solution of the freebase polymer inorganic solvent. This is followed by addition of anaqueous solution of a volatile acid wherein the solvent has highervolatility than the acid. The solvent is then distilled off so as toleave a solution in water of the salt form of the polymer. A suitablevolatile acid is acetic acid, in which event a suitable solvent isn-butyl acetate. The active ingredients particularly include detergentactives, including enzymes which are released during the wash cycle.

[0014] WO9220441 describes encapsulated particles comprising a coresurrounded by a coacervate coating that comprises a low criticalsolution temperature polymer and a water removal depressant for thetemperature of reversible insolubilisation of that polymer. Thecomposition is made by forming a dispersion of the water insoluble coreparticles in a solution of the polymer, heating the solution to cause itto precipitate as a coacervate, and then adding the depressant. Thecomposition can be an aqueous dispersion or dry particles. In thisprocess the LCST wall building material coacervates from the exterior.To prevent the encapsulated particles of the invention coagulating andsubsequently phase separating in the environment in which they are to beused, an entropic stabilising polymer, such as carboxymethyl cellulose,sodium alginates or starch, can be mixed with the LCST polymericcomponent prior to encapsulation. Such polymers can act as dispersantsin conditions of high salt concentration, e.g. in certain detergentenvironments.

[0015] Processes of forming capsules involving coacervation are known.Generally aminoplast capsules are formed by distributing a waterimmiscible liquid in an aqueous liquid containing the aminoplastprecursor, for instance a melamine formaldehyde resin. The capsule wallis formed by coacervation of the prepolymer onto on the droplets ofwater immiscible liquid. Thus the capsule wall is built up from theexterior by coacervation of the prepolymer from the aqueous continuousphase.

[0016] However, such processes are not useful when the material to beencapsulated is hydrophilic, especially an aqueous liquid. Variousattempts have been made to solve this problem. For instance in U.S. Pat.No. 4,157,983 capsules containing water-dispersible material are said toformed from an admixture of low HLB emulsifier, oily water-immisciblesolvent for the emulsifier urea-formaldehyde prepolymerwater-dispersible material, and water. This admixture is agitated toform a water-in-oil emulsion to which amphiphatic acidic catalyst isadded to cure the prepolymer. After curing to solid form, the capsulesare separated from the remaining liquid of the admixture. However, thisprocess has the disadvantage in that the prepolymer tends to coacervatesto form a matrix rather than capsules.

[0017] This problem was recognised in WO-A-9828975, which attempted toovercome the problem. The reference describes forming capsules byheating an emulsion containing an aqueous dispersed phase containing amelamine formaldehyde prepolymer. The problem is said to be overcome byincluding in the oil phase a surface active proton transfer catalystwhich is soluble in the organic liquid. Generally the proton transfercatalyst is an acidic material which is essentially oil soluble and atmost very slightly soluble in water. The proton transfer catalyst isusually a sulfonic acid having at least 20 carbon atoms in the molecule.

[0018] However, the presence of the proton transfer catalyst willinevitably affect the surface characteristics of the capsules that areformed. Thus it would be desirable to provide an alternative process forforming capsules by a reverse phase coacervation process, wherein thecapsules contain hydrophilic (especially aqueous material). It would bemore desirable to provide such a process which avoids the use of aproton transfer catalyst.

[0019] Although there are processes for encapsulating hydrophilic (egaqueous) materials described in the prior art, there is nonetheless aneed for an alternative processes. In particular there is a need for animproved process for making capsules by coacervation of water soluble orwater dispersible wall building materials.

[0020] Furthermore there is a need for products where the release of theaqueous core material can be controlled more reliably. Hence it is anobjective of the present invention is to provide shell core productswhich satisfy this requirement.

[0021] Furthermore all of the aforementioned references which providedelay release products wherein the release mechanism is suitable for usein a detergent composition are concerned with entrapment orencapsulation of large bulky entities, for instance enzymes or highermolecular weight active ingredients e.g. polymers. However, such delayrelease products are unsuitable for low molecular weight compounds, suchas monomeric acids, sequesterants and the like, since these compoundstend to be released slowly prior to use.

[0022] Therefore there is a need for a delay release product which iscapable of retaining low molecular compounds, such as acids, bases andsequesterants, and only released when a suitable trigger mechanism isemployed. In particular there is a need to a delay release product as acomponent of a detergent formulation, which product contains a lowmolecular weight additive, such as a buffering system or a sequesterant,wherein the additive is only released upon dilution of the detergentformulation. Preferably the additive should only be released immediatelyprior to or during a wash or rinse cycle.

[0023] Thus it is also an objective of the present invention is toprovide particles which contain entrapped low molecular weightingredients. In particular the invention is concerned with controllingthe release of additives in to a detergent system. Specifically it wouldbe desirable to provide a polymer entrapped buffering agents orsequesterants which only release the active ingredient immediately priorto or during the wash or rinse cycles. In particular it would desirableto provide such products where the additive is citric acid.

[0024] According to one aspect of the invention we provide a particulatecomposition comprising particles which consist of a shell wallsurrounding a hydrophilic core, wherein the shell wall is formed from apolymeric coacervate and wherein the particles comprise a polymericamphipathic stabiliser.

[0025] Furthermore we provide a novel process of producing a particulatecomposition comprising particles which consist of a shell wallsurrounding a hydrophilic core, comprising the steps of

[0026] a) forming an aqueous liquid that contains a wall buildingmaterial that is capable of forming the shell wall by coacervation,

[0027] b) dispersing the aqueous liquid into a water immiscible liquid,which comprises a stabilising substance to form a dispersion thatcomprises aqueous droplets dispersed in a continuous phase of waterimmiscible liquid,

[0028] c) subjecting the dispersion to coacervation conditions, suchthat the wall building material coacervates at the surface of theaqueous doplets, characterised in that the stabilising substancecomprises a polymeric amphipathic stabiliser.

[0029] The continuous phase may be any suitable water immiscible liquid.The water immiscible liquid may be a silicone oil, but is preferably ahydrocarbon, for instance a cyclic or straight chain aliphatichydrocarbon, typically having between 8 and 12 carbon atoms.

[0030] The presence of amphipathic polymeric stabiliser in the waterimmiscible liquid is essential for the successful formation of capsulesas opposed to a matrix of coacervate. A suitable stabiliser is desirablyformed from a monomer blend comprising a blend of an ethylenicallyunsaturated hydrophilic monomer and an ethylenically unsaturatedhydrophobic monomer. The polymeric stabiliser may be for instance acopolymer of ethylenically unsaturated polycarboxylic acid (includingdicarboxylic acid and the anhydrides) such as maleic acid or maleicanhydride. Preferably the stabiliser is a random copolymer of a blend ofhydrophobic monomers selected from styrene and alkyl (meth) acrylatesand hydrophilic monomers comprising ethylenically unsaturatedpolycarboxylic acid, i.e. an ethylenically unsaturated monomercontaining a multiplicity of carboxylic acids.

[0031] The stabilisers can be included in an amount up to 2% by weight,based on dry weight of prepolymer. More preferably the stabiliser isusually included in amounts between 0.1% to 1%, especially around 0.5%.This can improve the stability of the dispersion and may also lead to amore uniform particle size distribution. Typically the particles have asize of up to 1,000 microns, usually in the range 750 nanometers to 500microns, typically 100 to 200 microns.

[0032] During the process of coacervation the polymeric amphipathicstabiliser is thought to be in association with the surface of theaqueous droplets. This association may be a physical attraction or itcould be chemical bonding. It is possible that there is some covalentbonding that occurs although it is thought that any covalent bondingthat occurs is minimal. It is thought that it is more likely that thereis an association between the stabilser and the surface of the droplets.This ionic association is for instance an ionic association betweenionic groups on the stabiliser and ionic groups in the coacervate and/orthe coacervating prepolymer.

[0033] However, whatever the mechanism is responsible for the improvedcapsules obtained by the process, it is surprising that the presence ofthe polymeric amphipathic stabiliser in the water immiscible liquidactually prevents coacervation from occuring throughout the matrix ofthe particles. Thus formation of true capsules by this particular routeis unexpected.

[0034] Processes for providing true capsules containing a wall materialcontaining a coacervated shell wall, for instance an aminoplast resinhave usually only been made using an aqueous continuous phase and inwhich the shell wall building material is contained in the aqueouscontinuous phase. Thus generally in previous processes the shell wall isbuilt up from the outside.

[0035] The composition of the present invention comprises capsules andis desirably obtained by the reverse phase coacervation process of thepresent invention, in which a polymeric amphipathic stabiliser ispresent in a continuous water immmiscible liquid phase has notpreviously been contemplated. The particles of the present invention aredesirably prepared by a novel process in which the coacervate formingmaterials are dissolved in an aqueous discontinuous phase, which isdistributed throughout a non-aqueous continuous phase. Once thisdispersion is formed, the capsules may be conveniently formed byemploying suitable coacervation conditions.

[0036] Thus particles of the invention desirably consisting of ahydrophilic core material within an shell wall in which the shell wallis actually built up from within the particles. The particles formed bythe process preferably also comprise the polymeric amphipathicstabiliser located at the surface. Generally the stabiliser at leastpartially coats the shell wall. More preferably the polymericamphipathic stabiliser coats substantially all of the shell wall.

[0037] Thus in one aspect of the invention we provide a particulatecomposition comprising particles which consist of a shell wallsurrounding a hydrophilic core material, wherein shell wall is anaminoplast resin.

[0038] According to this form of the invention we provide a convenientprocess for providing the particulate composition. Thus according tothis aspect the aqueous phase comprises an aminoplast forming substance,for instance a melamine/formaldehyde prepolymer and active ingredient.This aqueous phase is dispersed into an water immiscible continuousphase to form a water in oil dispersion. The thus formed dispersion isstirred throughout the process in order to maintain the stability of thepolymerising particles. The dispersion should then be heated to at least50° C. for instance 60 and 90° C. for several hours thus formingparticles containing the active ingredient in a core which is surroundedby an aminoplast shell wall. Preferably the dispersion is heated tobetween 65 and 75° C. for between 2 and 3 hours. The dispersion ofaminoplast particles may be dehydrated using vacuum distillation toprovide substantially dry particles. When the shell wall is anaminoplast resin, it is generally formed from a prepolymer of ancompound containing at least two amide and/or amine groups with andaldehyde. Preferably the prepolymer is a urea formadehyde resin ormelamine formaldehyde resin. A particularly preferred prepolymer ismelamine formaldehyde resin Beetle PT 336. A suitable urea formaldehydeprepolymer can be formed by forming an aqueous solution of formaldehyde(e.g. 30 to 50% by weight) at a pH between 7 and 8 and combining withurea. The weight ratio of urea to formaldehyde is desirably between 1:6and 1:10, preferably about 1:8.

[0039] Alternatively the shell may be formed from a wall buildingmaterial which is a LCST (Low Critical Solution Temperature) polymer.Typically such polymers are fully soluble in water at relatively lowtemperatures. However, above a particular temperature the solution ofpolymer will phase separate into a polymer rich phase and a polymerdepleted phase. Generally the polymer rich phase will contain all or atleast most of the LCST polymer whilst the polymer depleted phase willcontain no or a lesser amount of the LCST polymer.

[0040] The LCST polymer can be a naturally occurring polymer such ascertain cellulose derivatives, such as the methyl, hydroxy propyl, andmixed methyl/hydroxy propyl cellulose ethers. However it is generallypreferred for the LCST polymer to be a synthetic polymer formed bypolymerisation of what can be termed an LCST monomer either as ahomopolymer or as a copolymer with a hydrophilic monomer that is presentin an amount insufficient to cause the LCST temperature to beunacceptably high. Suitable LCST monomers include N alkylacrylamide,N,N-dialkylacrylamide, diacetone acrylamide, N-acryloylpyrrolidine,vinyl acetate, certain (meth) acrylate esters (especially hydroxypropylesters), styrene, and various other vinyl monomers, especiallyNvinylimidazoline and the like.

[0041] When the LCST polymer is a copolymer, the comonomer is usuallyhydrophilic and can be non-ionic or ionic.

[0042] Suitable non-ionic monomers include acrylamide, hydroxyethylacrylate, vinyl pyrollidone, or hydrolysed vinyl acetate.

[0043] Anionic or cationic monomer can be used in place of or inaddition to the non-ionic comonomer to form a copolymer or terpolymerwith the LCST monomer respectively. Suitable anionic monomers includeethylenically unsaturated carboxylic or sulphonic acid monomers, forexample (meth) acrylic acid and alkaline salts thereof, and 2-acrylamidomethyl propane sulphonic acid. Suitable cationic monomers includedialkylaminoalkyl (meth)acrylates and acrylamides as acid addition orquaternary ammonium salts, for example dialkylaminoethyl (meth)acrylateacid addition salts.

[0044] A preferred LCST polymer is a polyvinyl alcohol prepared bypartial hydrolysis of polyvinyl acetate. The polyvinyl alcohol maycontain as much as 60% vinyl acetate units and thus would be consideredto have a relatively low degree of hydrolysis. Alternatively the degreeof hydrolysis may be as high as 95%, thus only contains 5% unhydrolysedvinyl acetate units. Preferably the degree of hydrolysis is between 60and 80%, preferably around 75%.

[0045] In this aspect of the invention the coacervation conditions willgenerally comprise elevating the temperature to above the criticalsolution temperature such that the polymer solution will phase separateas described above. In the process the polymer rich phase will occur atthe exterior of the particles. The LCST polymer will deposit at thesurface. As the process proceeds the LCST polymer deposits form acoherent film or membrane which becomes the capsule shell wall. Sincethe coacervation process involving an LCST polymer is frequentlyreversible, it will be generally necessary to stabilise the shell inorder to prevent it from redissolving or dispersing in the aqueousphase. Thus the shell wall can be made permanent. This is achieved mostdesirably by crosslinking the deposited LCST polymer. The crosslinkingprocess can be acheived by any multifunctional compound that can reactwith two or more functional groups that occur on the LCST polymer.Aldehydes have been found to be particularly effective for thecross-linking stage. A preferred aldheyde is glutaraldehyde.

[0046] In another form of the invention the wall building material is asalt of an ionisable polymer with a volatile counterion. Thus thepolymer may comprise free acid or free base groups and typically thecounterion is derived from a volatile compound.

[0047] Desirably the ionisable polymer is selected from polymers of anethylenically unsaturated free base amine, wherein the counterion isderived from a volatile acid, preferably acetate. When the ionisablepolymer contains a free base it is preferably formed from a co-polymerof (a) an ethylenically unsaturated hydrophobic monomer with (b) a freebase monomer of the formula

CH2=CR₁COXR₂NR₃R₄

[0048] where R₁ is hydrogen or methyl, R₂ is alkylene containing atleast two carbon atoms, X is O or NH, R₃ is a hydrocarbon group and R₄is hydrogen or a hydrocarbon group. The hydrocarbon group may be anystraight, branched or cyclic hydrocarbon group. It may be aromatic butis preferably aliphatic. Preferably R₃ is at least 4 carbon atoms. Morepreferably R₃ is t-butyl and R₄ is hydrogen. More preferably R₁ ismethyl, R₂ is ethylene and X is O.

[0049] We have found that polymers formed from the special combinationof hydrophobic monomer that are capable of forming a homopolymer ofglass transition temperature in excess of 50° C., preferably greaterthan 60 or 80° C. exhibit considerably improved performance in regard tothe impermeability to the fabric conditioner until the particles areexposed to a suitably dilute environment. By hydrophobic monomer we meanthat the monomer has a solubility in water of less than 5 g per 100 mlwater at 25° C.

[0050] Glass transition temperature (Tg) for a polymer is defined in theEncycopedia of Chemical Technology, Volume 19, fourth edition, page 891as the temperature below which (1) the transitional motion of entiremolecules and (2) the coiling and uncoiling of 40 to 50 carbon atomsegments of chains are both frozen. Thus below its Tg a polymer wouldnot to exhibit flow or rubber elasticity. The Tg of a polymer may bedetermined using Differential Scanning Calorimetry (DSC). Thus areference sample with known Tg and the experimental sample are heatedseparately but in parallel according to a linear temperature programme.The two heaters maintain the two samples at identical temperatures. Thepower supplied to the two heaters to achieve this is monitored and thedifference between them plotted as a function of reference temperaturewhich translates as a recording of the specific heat as a function oftemperature. As the reference temperature is increased or decreased andthe experimental sample approaches a transition the amount of heatrequired to maintain the temperature will be greater or lesser dependingon whether the transition is endothermic or exothermic. A typical plotindicating the glass transition temperature is shown in FIG. 1.

[0051] Alternatively the hydrophobic monomer can be any ethylenicallyunsaturated monomer which is insoluble in water, for instance generallyhaving a partition coefficient K between hexane and deionised water at20° C. of at least 5 and preferably at least 10.

[0052] A particularly preferred ionisable polymer includes a co-polymerof 55-85 weight % of methyl methacrylate with 15%-45% by weight tertiarybutylamino-ethyl methacrylate.

[0053] Alternatively the ionisable polymer may be selected from polymersof an ethylenically unsaturated free acids, wherein the counterion isderived from a volatile base, preferably ammonia or a volatile amine.Preferably the ionisable polymer is formed from a co-polymer of (a) anethylenically unsaturated hydrophobic monomer with (b) a free carboxylicacid monomer. The carboxylic acid monomer may be itaconic acid, maleicacid but is preferably either acrylic acid or methacrylic acid.

[0054] The hydrophobic monomer may be as defined above for the ionisablepolymer containing fee base groups. A preferred polymer is a co-polymerof 55-85 weight % of methyl methacrylate with 15%45% by weight ammoniummethacrylate. The coacervation conditions suitable for this polymerwould be the same as for the ionisable polymer containing fee basegroups. Suitably though the crosslinking process should be adapted sothat the cross-linking agent will readily react with functional groupsin the ionisable polymer, desirably groups that will react with freeacid groups. Suitably the cross-linking agent could includemultifunctional compounds containing epoxides, amines etc. Alterativelythe cross-linking agent may include multivalent metal ions, for instancecalcium, zirconium or aluminium.

[0055] The shell wall can be designed to have special releasecharacteristics. For instance the shell wall can be a semi-permeablemembrane and thus is permeable to water but not to larger molecules.Thus when these particles are expose to very concentrated exteriorenvironments the shell remains intact, but when the capsules are exposedto more dilute aqueous environments, for instance the wash water orrinse water in a laundry operation, there is a high osmotic pressure andwater will enter the capsules and the capsule wall will rupture.

[0056] Thus we provide a detergent composition comprising detergencybuilding ingredients and particles which consist of a shell wallsurrounding a core material, wherein the shell wall comprises ancoacervate polymer, especially an aminoplast resin and the core materialcomprises a water soluble active ingredient.

[0057] Furthermore, we have found that the shell walls comprising thecoacervate resin, preferably where this is an aminoplast polymer,prevent release of the low molecular weight active, until a suitabletrigger has occured. Thus the particles will retain the low molecularweight substance when the particles are contained in a detergentconcentrate, but rupture and release the active when exposed to the moredilute environment in the wash or rinse cycles.

[0058] The hydrophilic core material is preferably water soluble. Thecore material may be aqueous or anhydrous. More preferably the corecomprises a low molecular weight active, for instance a compound ofmolecular weight of less than 1,000. Normally the active is a compoundof considerably lower molecular weight, preferably below 500. Desirablythe active can be a solid but generally is a liquid at 25° C. Itgenerally has a solubility in water of at least 5 g/100 ml of water at25° C. and thus the active is normally soluble in the wash or rinsewater. The active may be inorganic but preferably is organic. It can be,for instance, a mineral acid but more usually comprises a carboxylicacid. Preferably the active ingredient comprises a buffering system,typically comprising a carboxylic acid and a base. More preferably theactive ingredient is a sequesterant or detergent buider, for instancediphosphate, triphosphate, phosphonate, citrate, nitrilotriacetic acid(NTA), ethylenediaminetetraacetic acid (EDTA),diethylenetriaminepentaacetic acid (DTMPA), alkyl- or alkenylsuccinicacid, soluble silicates or layered silicates (e.g. SKS-6 from Hoechst).The active ingredient includes other compounds containing at least twocarboxylic acid groups, and optionally amino groups. A particularlypreferred active is citric acid.

[0059] Alternatively the active ingredient may be a fabric conditioner,such as quaternary ammonium salts having only one long chain acyclicaliphatic hydrocarbon group (such as monostearyltrimethyl ammoniumchloride). Suitable fabric conditioners also include nonquaternaryamide-amines, such as the reaction product of higher fatty acids withhydroxy alkyl alkylene diamines, for instance reaction product of higherfatty acids and hydroxyethylethylenediamine (See “Condensation Productsfrom beta-Hydroxyethylethylenediamine and Fatty Acids or Their AlkylEsters and Their Application as Textile Softeners in Washing Agents,” H.W. Eckert, Fette-Seifen-Anstrichmittel, September 1972, pages 527-533).These materials are usually cited generically along with other cationicquaternary ammonium salts and imidazolinium salts as softening activesin fabric softening compositions. (See U.S. Pat. No. 4,460,485,Rapisarda et al., issued Jul. 17, 1984; U.S. Pat. No. 4,421,792, Rudy etal., issued Dec. 20, 1983; and U.S. Pat. No. 4,327,133, Rudy et al.,issued Apr. 27, 1982, all of said patents being incorporated herein byreference). U.S. Pat. No. 3,775,316, Berg et al., issued Nov. 27, 1973,incorporated herein by reference, discloses a softening finishingcomposition for washed laundry containing (a) the condensation productof hydroxyalkyl alkylpolyamine and fatty acids and (b) a quaternaryammonium compound mixture of (i) from 0% to 100% of quaternary ammoniumsalts having two long chain alkyl groups and (ii) from 100% to 0% of agermicidal quaternary ammonium compound. Desirably the fabricconditioners may be fabric softeners disclosed in EP 398137, U.S. Pat.No. 3,861,870, U.S. Pat. No. 4,308,151, U.S. Pat. No. 3,886,075, U.S.Pat. No. 4,233,164, U.S. Pat. No. 4,401,578, U.S. Pat. No. 3,974,076 orU.S. Pat. No. 4,237,016.

[0060] The particles can be designed to have particular releaserequirements. For instance it may be desirable that the particlesrelease the active ingredient in the wash cycle of a laundry operationonly. Alternatively it may be necessary that the active ingredient isonly released in the rinse cycle. This can be controlled by controllingthe thickness of the shell wall. The rate of release of the active canalso be controlled by the thickness of the shell wall.

[0061] The particles can also be modified by applying a coating to thesurface of the coacervate shell wall. Preferably the coating is anionisable polymer. For instance the coating may be a copolymer of anethylenically unsaturated hydrophobic monomer with an ethylenicallyunsaturated ionic monomer.

[0062] The coating may allow the release characteristics of theparticles to be varied. In addition particles containing a coating mayalso be more durable, for instance where the coacervate shell wall isrelatively thin.

[0063] Thus in one preferred aspect the particles comprise a shell wallwhich comprises a membrane of coacervate polymer, especially anaminoplast polymer, onto which has been coated an ionisable polymericresin. Thus the membrane is substantially impervious to the lowmolecular weight actives. However the membrane may allow the passage ofwater into the capsule. Thus in this instance the membrane issemipermeable.

[0064] The coating may typically be an ionisable polymer. Thus thepolymer may comprise free acid or free base groups and typically thecounterion is derived from a volatile compound.

[0065] Preferably the ionisable polymer coating is formed from aco-polymer of (a) an ethylenically unsaturated hydrophobic monomer with(b) a free base monomer of the formula

CH2=CR₁COXR₂NR₃R₄

[0066] where R₁ is hydrogen or methyl, R₂ is alkylene csontaining atleast two carbon atoms, X is O or NH, R₃ is a hydrocarbon group and R₄is hydrogen or a hydrocarbon group.

[0067] It is generally preferred that one of the hydrocarbon groups onthe nitrogen atom of the free base monomer is greater than 3 carbonatoms. Thus preferably R₃ is at least 4 carbon atoms. More preferablythe fabric conditioner is best retained when the R₃ is tertiary butyland R₄ is hydrogen. However R₃ may be other butyl or higher alkyl groupsor it may be other hydro-carbon groups containing at least 4 carbonatoms. R₃ can for instance be up to 30 carbon atoms or more, e.g.stearyl or lauryl. Generally effective results can be obtained usingshorter alkyl groups and so R₃ is usually not more than 8 carbon atoms.The t-butyl group is also advantageous because it seems to render themonomer units containing it more resistant to alkaline hydrolysis.

[0068] R₄ is frequently hydrogen but it can be alkyl such as methyl,ethyl or higher alkyl or it can be other hydro carbon group. The totalnumber of carbon atoms in R₃ and R₄ together is usually below 12, oftenbelow 8. R₂ is usually ethylene but it can be other linear or branchedalkylene group containing two or more (for instance 2-4) carbon atoms.R₁ is usually methyl.

[0069] X can be NH, with the result that the cationic monomer ispreferably a monoalkyl or dialkyl aminoalkyl (meth) acrylamide monomer,but preferably X is 0, with the result that the cationic monomer ispreferably a monoalkyl or dialkyl aminoalkyl (meth) acrylate.

[0070] The hydrophobic monomer may be a hydrophobic as definedpreviously with regard to the ionisable polymer used in the coacervationprocess. The hydrophobic monomer can be a water-insoluble alkyl ester ofmethacrylic acid or other aliphatic, water-insoluble monomer such asmethyl, ethyl or butyl acrylate or methacrylate. However the preferredhydrophobic monomers are for instance ethylenically unsaturated aromatichydrocarbon monomers, such as styrenes, preferably styrene or a methylstyrene. Thus preferably the hydrophobic monomer is selected from thegroup consisting of styrene, methylstyrene methyl methacrylate,acrylonitrile, tertiary butyl methacrylate, phenyl methacrylate,cyclohexyl methacrylate and isobornyl methacrylate.

[0071] The amount of the cationic monomer which should be used willdepend in part on the active ingredient which is entrapped within themonomer. The proportion of cationic free based monomer should be suchthat there is little or no release of the active ingredient duringexposure to the wash water but that there is significant swelling andrelease of the active ingredient upon exposure to the wash or rinsewater.

[0072] The degrees of swelling which will result in retention or releaseof the active ingredient depend in part on the molecular size of theactive ingredient, in that good retention of an active ingredient ofsmall molecular size requires that the polymer should be less swollen(when exposed to the detergent concentrate or wash water) than when theactive ingredient has a higher molecular size. Similarly, good releasewhen exposed to rinse water requires a higher degree of swelling forhigher molecular size active ingredients than for lower molecular sizeactive ingredients.

[0073] Generally the amount of cationic monomer will be within the range5-30 mole % or 10-50 weight %. When, as is preferred, the free basemonomer is t-butylaminoethyl methacrylate and the hydrophobic monomer isstyrene, methyl styrene or methyl methacrylate, the amount of cationicmonomer is preferably from 15%-45% by weight, most preferably around30%-40% by weight.

[0074] The coating can be formed of recurring units of monomersconsisting solely of the hydrophobic monomer and the free base cationicmonomer but if desired minor amounts of other monomers may be included.

[0075] The coating on the coacervate shell wall may be provided forinstance by the following steps,

[0076] A) dispersing the uncoated particles into a water immiscibleliquid, optionally containing an amphipathic polymeric stabiliser.

[0077] B) providing an aqueous solution containing a volatile solvent ofa polymeric salt formed from a monomer blend which comprises saidhydrophobic monomer and said free base monomer, which polymeric saltcomprises a volatile counterion component,

[0078] C) dispersing the polymer solution into the water immiscibleliquid phase of A), and

[0079] D) subjecting the dispersion to dehydration wherein water isevaporated from the aqueous particles thereby forming ionisable polymercoated particles, wherein the volatile counterion component of the saltis evaporated during the distillation and the matrix polymer isconverted to its free base form.

[0080] Desirably the process also employs a polymeric amphipathicstabiliser in the water immiscible liquid. The amphipathic stabilisermay be a stabiliser already defined herein.

[0081] In the process of the present invention the dehydration step canbe achieved by any convenient means. Desirably dehydration can beeffected by subjecting the dispersion in oil to vacuum distillation.Generally this will require elevated temperatures, for instancetemperatures of 30° C. or higher. Although it may be possible to usemuch higher temperatures e.g. 80 to 90° C. it is generally preferred touse temperatures of below 60 or 70° C.

[0082] Instead of vacuum distillation it may be desirable to effectdehydration by spray drying. Suitably this can be achieved by the spraydrying process described in WO-A-97/34945.

[0083] The dehydration step removes water from the aqueous solution ofmatrix polymer and also the volatile counterion component, resulting ina dry polymer matrix which is insoluble an non-swellable in water,containing therein the fabric conditioner which is distributedthroughout the polymeric matrix.

[0084] This process results in products which have enhancedeffectiveness in that the polymer matrix which does not allowsubstantially any of the entrapped active ingredient to be releasedexcept when diluted, for instance immediately prior to or during thewash or rinse cycles of the laundry operation.

[0085] Alternatively the polymeric coating may be formed around thecoacervate shell walls, for instance by a coacervation technique asdescribed in EP-A-356239 or WO-A-92/20771 or, preferably, by interfacialcondensation as described in, for instance, WO-A-97/24179. Preferablythe particles have a shell (around the core) of a polyamide or othercondensation polymer, preferably formed by interfacial condensation.

[0086] The polymeric coating can be further enhanced by including across-linking step in the process. This can be achieved by includingself cross-linking groups in the polymer, for instance monomer repeatingunits carrying a methylol functionality. Preferably though thecross-linking is achieved by including a cross-linking agent with theionisable polymer. The cross-linking agent are generally compounds whichreact with functional groups on the polymer chain.

[0087] The cross-linking process desirably occurs during the dehydrationstep. Thus where a cross-linking agent is included, it will generallyremain dormant until the dehydration is started.

[0088] Generally the ionisable coating polymer may be prepared by anysuitable polymerisation process. For instance the polymer can beconveniently prepared by aqueous emulsion polymerisation for instance asdescribed in EP-A-697423 or U.S. Pat. No. 5,070,136. The polymer canthen be neutralised by the addition of an aqueous solution of ammoniumhydroxide or a volatile amine.

[0089] Generally the coating polymer has a molecular weight of up to200,000 (Determined by GPC using the industry standard parameters).Preferably the polymer has a molecular weight of below 50,000, forinstance 2,000 to 20,000. Usually the optimum molecular weight for thematrix polymer is around 8,000 to 12,000.

[0090] Typically the monomer blend may contain at least 50% by weighthydrophobic monomer, the remainder being made up of anionic monomer.Generally though the hydrophobic monomer will be present in amounts ofat least 60% by weight.

[0091] The particles may be dispersed in a liquid detergent, forinstance by blending a dispersion of particles (usually afterdehydration) in a surfactant or in another water-immiscible liquid or inan water-immiscible liquid into the liquid detergent. Alternatively theparticles may be distributed throughout solid detergent tablets or adetergent powder formulation. Thus in one preferred aspect of theinvention we provide a detergent composition, which may be for instancein the form of a liquid detergent concentrate or a detergent tablet inwhich the particles are dispersed or distributed throughout thedetergent composition and in which low molecular weight activeingredient is not released in the detergent composition but is releasedduring the wash or rinse cycles of said laundry operation.

[0092] Typically the detergent composition comprises one or moresurfactants, each of which may be anionic, non-ionic, cationic, orzwitterionic. The detergent will usually contain 0-50% of anionicsurfactant such as linear alkylbenzenesulfonate (LAS),alpha-olefinsulfonate (AOS), alkyl sulfate (fatty alcohol sulfate) (AS),alcohol ethoxysulfate (AEOS or AES), secondary alkanesulfonates (SAS),alpha-sulfo fatty acid methyl esters, alkyl- or alkenylsuccinic acid, orsoap. It may also contain 0-40% of non-ionic surfactant such as alcoholethoxylate (AEO or AE), carboxylated alcohol ethoxylates, nonylphenolethoxylate, alkylpolyglycoside, alkyldimethylamine oxide, ethoxylatedfatty acid monoethanolamide, fatty acid monoethanolamide, or polyhydroxyalkyl fatty acid amide (e.g. as described in WO 92/06154).

[0093] The detergent may comprise one or more polymers. Examples arecarboxymethylcellulose (CMC), poly(vinylpyrrolidone) (PVP),polyethyleneglycol (PEG), poly(vinyl alcohol) (PVA), polycarboxylatessuch as polyacrylates, maleic/acrylic acid copolymers and laurylmethacrylate/acrylic acid copolymers.

[0094] The detergent may contain a bleaching system which may comprise aH₂O₂ source such as perborate or per carbonate which may be combinedwith a peracid-forming bleach activator such astetraacetylethylenediamine (TAED) or nonanoyloxybenzenesulfonate (NOBS).Alternatively, the bleaching system may comprise peroxyacids of, e.g.,the amide, imide, or sulfone type.

[0095] The detergent, if built, may contain 1-65% of a detergent builderor complexing agent such as zeolite, diphosphate, triphosphate,phosphonate, citrate, nitrilotriacetic acid (NTA),ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaaceticacid (DTMPA), alkyl- or alkenylsuccinic acid, soluble silicates orlayered silicates (e.g. SKS-6 from Hoechst). In accordance with thepresent invention the detergent builder is an active ingrediententrapped within the aminoplast particles.

[0096] The detergent composition may be stabilized using conventionalstabilizing agents, e.g. a polyol such as propylene glycol or glycerol,a sugar or sugar alcohol, lactic acid, boric acid, or a boric acidderivative such as, e.g., an aromatic borate ester, and the compositionmay be formulated as described in, e.g., WO 92/19709 and WO 92/19708.

[0097] The detergent may also contain other conventional detergentingredients dyes, bactericides, optical brighteners, or perfume.

[0098] The following examples illustrate the invention.

EXAMPLE 1

[0099] Preparation of Aminoplast Capsules

[0100] An aqueous phase comprising the citric acid (40 g), water (60 g)and a Melamine/Formaldehyde resin Beetle PT336 (20 g) were mixed. An oilphase prepared by mixing an isoparaffinic solvent (isopar G, 300 g) andan amphipathic polymeric stabiliser (2 g). The aqueous and oil phasesmixed to form a water in oil dispersion. The dispersion was heated to70° C. for three hours and the dispersion was dehydrated using vacuumdistillation. The beads were recovered by filtration and air dried.

[0101] Coating the Aminoplast Capsules

[0102] The coating polymer comprising 35 weight % tertiary butyl aminoethyl methacrylate and 65 weight % methyl methacrylate was preparedthermally in alcoholic solvent at 35% active content. The molecularweight of the polymer was 25-30 000. Water containing acetic acid wasadded and the alcoholic solvent removed via vacuum distillation and thepolymer converted to the amine-acetate form.

[0103] The product of example 1 were redispersed in Isopar isoparaffinicsolvent. The coating polymer and butyl acetate was mixed into thedispersion. The dispersion was then subjected to vacuum distillationuntil the solvent was removed. Once all solvent removed, the beads wererecovered by filtration and air dried.

EXAMPLE 3

[0104] Evaluation studies showed that the products of examples 1 and 2did not release any citric acid in a liquid detergent concentrate, butthat on dilution analogous to the water in the wash cycle, completerelease of the citric acid was achieved.

EXAMPLE 4

[0105] Preparation of Urea Formaldehyde Aminoplast Capsules

[0106] An aqueous solution of formaldehyde (74 g of a 37% weight/volume)is prepared and the pH was adjusted to 7.5 using sodium hydroxide. Urea(4 g) is combined with this solution. The mixture is poured into asuspending medium of liquid paraffin (1,100 ml) including Span 85emulsifier (40 ml) and petroleum ether (50 ml bpt range 100-120° C.).The mixture was heated and maintained at a temperature of 82° C. for 2hours, whilst being stirred and maintained under a nitrogen atmosphere.The product was then acidify to pH 5 using acetic acid and stirred for afurther 16 hours. The beads were decanted off and washed with a mixtureof water and acetone. The beads were then post cured by mixing withammonium chloride (6% w/w) at 105° C. for 17 hours. The resulting beadswere wash with a mixture of water and acetone and then dried undervacuum.

EXAMPLE 5

[0107] Preparation of Urea Formaldehyde Aminoplast Capsules ContainingCitric Acid

[0108] Example 4 was repeated except that 6 g of citric acid wasincluded into the aqueous phase.

[0109] Evaluation studies indicated that all of the citric acid had beenencapsulated and that non of the citric acid was released in a highelectrolyte environment analogous to a detergent concentrate. Furtherevaluation showed that the capsules ruptured and that all of the citricacid was released when the capsules were subjected to a more diluteaqueous environment as in wash water or rinse water.

EXAMPLE 6

[0110] Preparation of Microcapsules by Coacervation from LCST Polymer

[0111] An aqueous phase is prepared by dissolving 0.1 g of a blue dyeinto 100 g of polyvinyl alcohol solution at 10% solids (Gohsenol KP08).This is added to an oil phase comprising 1.7 g of 30% amphipathicstabiliser (random copolymer of ethylenically unsaturated hydrophobicand hydrophilic monomers as defined herein) and 300 g of a hydrocarbonoil under mechanical agitation at 22° C. After 5 minutes agitation,droplets of aqueous phase are formed having a mean particle diameter ofaround 200 microns. The temperature of the water-in-oil emulsion israised to 60° C. to introduce polyvinyl alcohol coacervation to form acoating at the water-oil interface. The mixture is maintained at 60° C.for 30 minutes to complete the coacervate coating process. The polyvinylalcohol coacervate is then hardened by adding 5 ml of 50% glutaraldehydesolution and keeping the mixture for 2 hours at 60° C. and then afurther hour at 80° C. tro complete the cross-linking reaction.

[0112] The microcapsule suspension in oil is cooled and themicrocapsules recovered by filtration. The microcapsules were thenexamined under a light microscope and the presence of the core shellstructure was clear apparent.

1. A particulate composition comprising particles which consist of ashell wall surrounding a hydrophilic core, wherein the shell wall isformed from a polymeric coacervate and wherein the particles comprise apolymeric amphipathic stabiliser.
 2. A composition according to claim 1in which the polymeric amphipathic stabiliser is formed bycopolymerising at least one hydrophilic ethylenically unsaturatedmonomer with at least one hydrophobic ethylenically unsaturated monomer.3. A composition according to claim 1 or claim 2 in which the polymericamphipathic stabiliser at least partially coats the shell wall.
 4. Acomposition according to any of claims 1 to 3 in which the shell wallcomprises an aminoplast resin.
 5. A composition according to any ofclaims 1 to 4 in which the shell wall is formed from a compoundcontaining at least two amide and/or amine groups and an aldehyde,preferably selected from a urea formadehyde resin and a melamineformaldehyde resin.
 6. A composition according any one of claims 1 to 5in which the shell wall is formed from an LCST polymer, preferably apolyvinyl alcohol prepared by partial hydrolysis of polyvinyl acetate.7. A composition according to any of claims 1 to 6 in which thepolymeric coacervate is cross-linked.
 8. A composition according to anyof claims 1 to 7 in which the shell wall is formed from a salt of anionisable polymer with a volatile counterion, wherein the ionisablepolymer is selected from polymers of (i) an ethylenically unsaturatedfree base amine and in which the counterion is derived from a volatileacid, preferably acetate, (ii) in which the ionisable polymer isselected from polymers of an ethylenically unsaturated free acids,wherein the counterion is derived from a volatile base, preferablyammonia or a volatile amine.
 9. A composition according to claim 8 inwhich the ionisable polymer is formed from a co-polymer of (a) anethylenically unsaturated hydrophobic monomer with (b) either (i) a freebase monomer of the formula CH2=CR₁COXR₂NR₃R₄  where R₁ is hydrogen ormethyl, R₂ is alkylene containing at least two carbon atoms, X is O orNH, R₃ is a hydrocarbon group and R₄ is hydrogen or a hydrocarbon groupor (ii) a free carboxylic acid monomer.
 10. A composition according toclaim 9 in which R₄ is hydrogen, R₃ is at least 4 carbon atoms,preferably t-butyl, in which R₁ is methyl, R₂ is ethylene and X is 0.11. A composition according to claim 9 in which the free carboxylic acidmonomer is acrylic acid or methacrylic acid.
 12. A composition accordingto any of claims 9 to 11 in which the hydrophobic monomer is selectedfrom the group consisting of monomers which are capable of forming ahomopolymer of glass transition temperature in excess of 50° C.
 13. Acomposition according to any of claims 9 to 12 in which the hydrophobicmonomer is selected from the group consisting of styrene, methylmethacrylate, acrylonitrile, tertiary butyl methacrylate, phenylmethacrylate, cyclohexyl methacrylate and isobornyl methacrylate.
 14. Acomposition according to any of claims 9 to 13 in which the polymer is aco-polymer of 55-85 weight % of methyl methacrylate with 15%45% byweight tertiary butylamino-ethyl methacrylate.
 15. A compositionaccording to any of claims 9 to 13 in which the polymer is a co-polymerof 55-85 weight % of methyl methacrylate with 15%45% by weight ammoniummethacrylate.
 16. A composition according to any of claims 1 to 15 inwhich the particles are coated by an ionisable polymer.
 17. Acomposition according to claim 16 in which the ionisable polymer is apolymeric salt formed from a monomer blend which comprises saidhydrophobic monomer and a salt of a free base monomer with a volatilecounterion.
 18. A composition according to any of claims 1 to 17 inwhich the particles are 90% by weight below 30 microns.
 19. Acomposition according to any of claims 1 to 18 in which the corematerial is aqueous.
 20. A composition according to any of claims 1 to19 in which the core material comprises a low molecular weight activeingredient.
 21. A composition according to any of claims 1 to 20 inwhich the active ingredient has a molecular weight less than 1,000,preferably less than
 500. 22. A composition according to any of claims 1to 21 in which the core material comprises a buffering system and/or asequesterant and/or detergent builder.
 23. A process according to any ofclaims 1 to 22 in which the core material comprises citric acid.
 24. Aprocess of producing a particulate composition comprising particleswhich consist of a shell wall surrounding a hydrophilic core, comprisingthe steps of a) forming an aqueous liquid that contains a wall buildingmaterial that is capable of forming the shell wall by coacervation, b)dispersing the aqueous liquid into a water immiscible liquid, whichcomprises a stabilising substance to form a dispersion that comprisesaqueous droplets dispersed in a continuous phase of water immiscibleliquid, c) subjecting the dispersion to coacervation conditions, suchthat the wall building material coacervates at the surface of theaqueous droplets, characterised in that the stabilising substancecomprises a polymeric amphipathic stabiliser.
 25. A process according toclaim 24 in which the polymeric amphipathic stabiliser is formed bycopolymerising at least one hydrophilic ethylenically unsaturatedmonomer with at least one hydrophobic ethylenically unsaturated monomer.26. A process according to claim 24 or claim 25 in which the polymericamphipathic stabiliser is in association with the surface of the aqueousdroplets during step (c).
 27. A process according to any of claims 24 to26 in which the polymeric amphipathic stabiliser at least partiallycoats the shell wall.
 28. A process according to any of claims 24 to 27in which the wall building material is an aminoplast prepolymer and theshell wall comprises an aminoplast resin.
 29. A process according toclaim 28 in which the wall building material is a compound containing atleast two amide and/or amine groups with and aldehyde, preferablyselected from a urea formadehyde resin and a melamine formaldehyderesin.
 30. A process according to claim 28 or claim 29 in which thecoacervation conditions comprise elevating the temperature of thedispersion to above 50° C. sufficient for the wall building material toform an aminoplast resin.
 31. A process according any one of claims 24to 27 in which the wall building material is a LCST polymer, preferablya polyvinyl alcohol prepared by partial hydrolysis of polyvinyl acetate.32. A process according to claim 31 in which the coacervation conditionscomprise elevating the temperature of the dispersion to above thecritical solution temperature, such that the LCST polymer deposits atthe surface of the aqueous droplets thus forming a shell and thenstabilising the shell, preferably by cross-linking.
 33. A processaccording to any of claims 24 to 27 in which the wall building materialis a salt of an ionisable polymer with a volatile counterion.
 34. Aprocess according to claim 33 in which the ionisable polymer is asdefined by any of claims 9 to
 15. 35. A process according to claim 33 or34 in which the coacervation conditions comprise elevating thetemperature of the dispersion sufficient to remove the volatilecounterion, such that the ionisable polymer deposits at the surface ofthe aqueous droplets thus forming a shell and then optionallystabilising the shell, preferably by cross-linking.
 36. A processaccording to any of claims 24 to 35 in which the particles are coated byan ionisable polymer.
 37. A process according to claim 36 in which theparticles are coated by following steps, A) dispersing the uncoatedparticles into a water immiscible liquid, optionally containing anamphipathic polymeric stabiliser thereby forming a dispersion, B) addingto the providing an aqueous solution containing a salt of an ionisablepolymer with a volatile counterion, C) dispersing the polymer solutioninto the water immiscible liquid phase of step A), and D) subjecting thedispersion to dehydration wherein water is evaporated from the aqueousparticles thereby forming ionisable polymer coated particles, whereinthe volatile counterion component of the salt is evaporated during thedistillation and the ionisable polymer is converted to its free base oracid form.
 38. A process according to claim 37 in which the ionisablepolymer is a polymeric salt formed from a monomer blend which comprisessaid hydrophobic monomer and a salt of a free base monomer with avolatile counterion.
 39. A process according to any of claims 24 to 38in which the water immisible liquid is a hydrocarbon or a silicone oil.40. A process according to any of claims 24 to 39 in which the particlesare as defined in any of claims 1 to
 23. 41. A liquid detergentconcentrate or a solid detergent tablet comprising a composition definedin any of claims 1 to 23 or obtainable by the process of any of claims24 to 40 and wherein the hydrophilic core material is not released inthe concentrate but is released during the wash or rinse cycle of alaundry operation.